PLant form and functions (3)

Question 1

What are the functions of sieve tube elements?

Answer 1

-Food-conducting cells
-Present in phloem tissue
-Sieve-tube elements remain alive at maturity, although they lose most of their organelles, including the nucleus and ribosomes.
-This reduction in cell contents with maturity enables nutrients to pass more easily through the cell.

Question 2

What are the kinds of growth that differentiate plants and animals?

Answer 2

Most animals are characterized by determinate growth, stopping growth after a certain size.

Most plants have indeterminate growth, continuing to grow throughout a plant’s life.

Question 3

How are plants categorized based on the length of their life cycles?

Answer 3

-Annuals complete their life cycle in one year.
-Biennials complete their life cycle in two years.
-Perennials live for many years.

Question 4

Plant growth originates in _________, areas of unspecialized, dividing cells.

Answer 4

Plant growth originates in meristems, areas of unspecialized, dividing cells.

Question 5

What is primary growth?

Answer 5

Primary growth lengthens the plant, be it from the terminal buds, the axillary buds, or the root tips

Question 6

How do apical meristems initiate primary growth?

Answer 6

Apical meristems at the tips of roots and in terminal buds and axillary buds of shoots initiate primary growth by producing new cells

Question 7

What is the root cap and what is its function?

Answer 7

Looking at primary growth from the root, the root tip is covered by a root cap that protects actively dividing cells of the apical meristem.

Question 8

How does growth in length occur behind the root tip?

Answer 8

Growth in length occurs just behind the root tip, where three zones of cells at successive stages of primary growth are located.

Question 9

What are the 3 zones of cells of primary growth?

Answer 9

Zone of cell division, zone of elongation, zone of differentiation.

The three zones of cells overlap, with no sharp boundaries between them.

Question 10

The zone of cell division includes the _____ and the ____. What happens in this zone?

Answer 10

The zone of cell division includes the root apical meristem and cells that derive from it.

New root cells are produced in this region, including the cells of the root cap.

Question 11

What happens in the zone of elongation?

Answer 11

In the zone of elongation, root cells grow longer.

-It is the cell elongation in this zone that pushes the root tip deeper into the soil.
-The cells lengthen because of the parallel arrangement of circular bands of cellulose fibers in their cell walls

Question 12

What occurs in the zone of differentiation?

Answer 12

The three tissue systems of a mature plant (dermal, ground, and vascular) complete their development in the zone of differentiation.

Question 13

Cells of the vascular cylinder differentiate into _____ and ____

Answer 13

Cells of the vascular cylinder differentiate into primary xylem and primary phloem.

Question 14

Explain the primary growth in the apical meristem in the shoot.

Answer 14

Dividing cells are located at the tip of the terminal bud.

Elongation occurs just below this meristem, and the elongating cells push the apical meristem upward, instead of downward as in the root.

As the apical meristem advances upward, some of its cells remain behind, and these become new axillary bud meristems at the base of the leaves.

Question 15

What is secondary growth and where does it arise from?

Answer 15

An increase in a plant’s diameter (secondary growth) arises from cell division in a cylinder of meristem cells called the vascular cambium

Question 16

How does the vascular cambium thicken the stem?

Answer 16

The vascular cambium thickens a stem by adding layers of secondary xylem, or wood, next to its inner surface.

Outside the vascular cambium, the bark includes secondary phloem (produced by vascular cambium), cork cambium, and protective cork cells produced by the cork cambium

Question 17

Secondary growth increases the _______ of woody plants

Answer 17

Secondary growth increases the diameter of woody plants.

Question 18

Explain the two types of cambium.

Answer 18

1. Cork Cambium: building outer layers of bark, grows outward and builds dermal tissue system
2. Vascular Cambium : growing new vascular tissue system.

• if the cells grow outward, secondary phloem is being created
• if the cell is growing inward, secondary xylem is being created

Question 19

What is the heartwood of a tree? Why is it resistant to rotting?

Answer 19

The heartwood, in the center of the trunk, consists of older layers of secondary xylem.

These cells no longer transport water; they are clogged with resins and other compounds that make heartwood resistant to rotting

Question 20

What does colour of the heartwood tell you?

Answer 20

The lighter-colored sapwood is younger secondary xylem that does conduct xylem fluid .